The field of the present invention is hot water supply systems employing solar energy.
With the increasing scarcity of fossil fuels and the particular supply problems experienced over the past years by the United States, a plurality of other forms of energy have gained wide attention. One of the most important areas of new interest is solar energy. Solar energy has been particularly of interest for use in heating buildings and potable water. Often, such solar energy systems incorporate mechanisms for heating water which may then be stored and used as both the source of heat and a source of hot water. Such systems generally include a solar panel or panels having an array of tubes for heating water contained within the tubes. Storage tanks are also employed to save the heat energy thus obtained. Boilers are often commonly employed to augment the solar energy source during times of darkness and inclement conditions.
Certain difficulties have been experienced with solar systems which have inhibited the adoption of such systems. A first problem is initial cost. It remains difficult to justify the initial expense of many solar systems because the lifetime expense of conventional fossil fuel systems remains less. Consequently, a major effort in the solar energy industry has been to improve the efficiency of the solar energy systems to make them more competitive with more conventional heating and water heating systems.
Another difficulty which has been experienced with solar energy systems is in harsh environments where the potential for the water with the solar panel to freeze is substantial. Because the solar panels are designed to pick up as much heat as possible during daytime hours, they are highly susceptible to giving off substantial heat during cold and dark periods. Thus, the relatively exposed tubes filled with water are likely to freeze. One solution has been to drain the panels. However, draining the system is not generally preferred.
Another problem that has been encountered in solar energy systems is that that the designs of the panels for maximum efficiency are at times in conflict with the durability required of such panels which must be exposed much if not all of the time to the environment. One particularly efficient panel design incorporates thin films of plastic material best suited for durability, light transmissivity and heat opacity. This system incorporates two thin films as will be more fully described in the preferred embodiment herein. However, difficulties have been experienced in mounting these films to achieve the proper strength and durability and to meet sealing requirements.
Finally, the advent of new and varied solar energy systems have come into conflict with the building codes in the United States. Building codes have been developed to promote maximum safety and maximum durability of structures. Consequently, the solar energy industry has had to pay particular attention to the myriad codes which exist and conform to these codes which have generally been formulated without much attention to solar energy needs and designs.